\begin{abstract}
Most programmers believe that parallel programming is harder than sequential programming.
Many also believe that today's parallel programming systems make it even harder.
We have developed a suite of chained toy problems that can be used to assess
the usability of different scientific programming languages, parallel or otherwise.
This paper motivates and describes the suite,
and discusses what we have learned from porting it to four parallel C++ systems
(MPI, OpenMP, Intel Thread Building Blocks, and a Linux tuple space system),
and from translating it into sequential and parallel Haskell.
\end{abstract}
